2. The SSL Exception warning is not to confuse with the "Server not found" warning/message.
3. When you first visit the secure socket layer (ssl) "version" of hackerspace.lu, the content won't change. The only thing that changes is that **any** data sent and received between the site and the client (you) is being encrypted and though secured. To enable this, you need to add the valid Certificate to your browser, in this case Mozilla's FireFox.
4. To get on, you need to click on "I understand the risks." and confirm by "add exception".
5. A new window will pop-up. It'll take a few seconds to get the certificate, or you just click on "Get certificate" and confirm by "Confirm Security Exception", please ensure that the "Permanently store this exception".
After finishing the last step, the site will reload in SSL-Mode and you'll probably receive another (last) warning message. By confirming the the warning with "OK" this warning won't show again, by enabling the little box, everytime the condition mentioned in the window is raised, the window pop-up will occur.